As shown in FIG. 1, a pressurized injector of the prior art comprises a barrel 1A and a pressurized container 1B which is detachably fastened with a starting end "B" of the barrel 1A. The barrel 1A is provided with an injecting end "A" opposite to the starting end "B". The barrel 1A is provided therein with a piston 4A. The barrel 1A contains a construction filling material, which is forced out of the injecting and "A" by the piston 4A which is acted on by the pressure of gas contained in the pressurized container 1B.
Such a prior art injector as described above is defective in design in that it is vulnerable to gas leak in the event that the pressurized container 1B is not securely engaged with the starting end "B" of the barrel 1A in the wake of the adding of a filling material. If the filling material is added to the barrel 1A from the injecting end "A" of the barrel 1A, the piston 4A is vulnerable to being forced out of the starting end "B" of the barrel 1A by the excess pressure of the filling material.